MDF "Forbidden"

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(l_shearer) #1

Continuing the discussion from Laser Cutter - Trotec Speedy 300:

Dear interested parties,

I am a little confused why MDF is on the banned list of materials.
Apart from acrylic (which is at least 4x the cost), 3 to 6mm MDF is usually the backbone of craft and prototype lasercutting in my limited but international experience.

Sources indicating it can be cut;


Opinion:


I think that the main rationales for Forbidding materials would presumably be that they are known to either;

  • Pose an unacceptable risk of fire or damage to the equipment
  • Generate known dangerous fumes which exceed our ability to ventilate

An example of the former would be styrene or polystyrene; it tends to melt and catch fire rather than cut or engrave, and has destroyed many other space’s cutters
An example of the latter would be chlorinated plastics, such as Polyvinyl Chloride (“vinyl” and “PVC”)

Some materials may need additional precautions; for example,

  • Many woods (including hardwoods) may be oily and pose additional fire risk
  • Engineered materials (Plywood, MDF) which often have glues mixed in; these are not necessarily dangerous but can cut poorly compared to (for instance) pure birch
  • Rubber, which may or may not contain chlorine
  • Multi-component items like foam core and Depron, where different layers burn at different rates
  • Many cloths and leathers can be cut or etched, but again some materials must be avoided for fire or fume reasons (e.g. “pleather”)

Qualifiers like “Laser Grade” Plywood should probably be avoided.
Although it may indicate that it cuts better than a plywood with thicker glue or different wood, blanket exclusion of non- “laser grade” materials is misleading.

Materials of similar quality but sold from non-laser shops can meet or exceed expectations. Specifically, there is no one quality that defines a plywood as “laser grade” - it is a combination of the exterior and interior layers quality, grain, thickness, number of knots; the number of layers; the amount and type of glue (phenolic glues take 4x as long to cut);

I would highly recommend reading this blog post from a small-scale manufacturer who do this all the time. Their puzzles are cool

Some materials cut so poorly that warning makers against use is necessary
Materials that do not pose an equipment safety or toxic fume risk are reasonable to list as a “does not cut”, for example;

  • Polycarbonate; tends to warp and discolour
  • Gold coated mylar, IR reflective surfaces (Like copper on PCB)

This is not to say that it can’t be cut; I have personally etched PCBs using a laser cutter and spray-on paint, and some reflective surfaces like the backs of common, non-first-surface) mirrors can be etched off to great effect.

Why MDF might not be cut in the space


I obviously don’t know the full story here. But here are some concerns I can guess;

  • MDF fibres are believed to cause a health risk
  • Partially true. They mostly pose an issue with chronic exposure (i.e. professional)
  • Yes, there is generally formaldehylde in MDF. The amount is extremely limited if you buy your MDF in the EU
  • Almost all the risk comes softwood and hardwood particulate matter, which comes from sanding and machining MDF, not burning it
  • Local exhaust ventilation and vacuuming with a HEPA filter equipped vacuum cleaner is the general requirement
  • Please read This helpful FAQ from your government
  • The experience on the previous iteration of our laser cutter was unsatisfactory / it did not cut
  • But surely this is an issue with either the setup, or an issue of “does not cut” rather than “forbidden from cutting”.
  • Do trotted really want public documentation that they have supplied the only lasercutter in the UK that I can find upon which MDF is Forbidden?
  • It smells bad / awful
  • But so does brewing beer, and we haven’t complained to the council about Canopy yet
  • Bad smell does not mean a toxic fume issue. Gangrene smells bad. Sewerage smells bad. Low levels of hydrogen sulphide (up to about 10ppm) smell Awful. None of those smells pose any toxic, fume related effects.

Proposal


  1. The reasoning for forbidding MDF be put forward and debated, and documented.
  2. In the absence of meeting an agreed threshold for being forbidden, the status of MDF be revised to;
  • MDF up to 4mm be listed on the “Permitted materials” list
  • MDF from 5 - 18mm be listed as “Use with additional precautions (Fire risk)”
  • MDF >18mm be listed as “Does not cut” (But can be engraved)

Cheers guys.

List of Inducted Members

(laurent_muchacho) #2

I think you’ll get the official reply but the quick answer is that cutting MDF create a lot of smoke and will clog the filter much faster and it will mean that we’ll have to replace the filter much sooner than planned and obviously don’t have the money to do so yet.

As you stated there is many source where MDF is listed as being OK to cut on the laser cutter and I saw our laser cutter cutting MDF. Unfortunately the decision didn’t came down to fire risk but to pure maintaining cost.

ps: please feel free to correct me if I’m wrong as this is what I caught up between discourse chat and person to person chat


(Tom Lynch) #3

MDF and non-laser ply, anything with glue or resin in it will block the filter faster than you can say Makerspace.

We did a test, on a project early on and the machine became very dirty, much of the brown discolouration is because of that project. The machine was very sticky inside also. This also increases the risk of breaking the lens from residue on the lens that needs cleaning off.

Importantly: The fumes from the MDF go through the filter into the room leaving an acrid smell that I found left me with itchy skin and eyes, sore throat, triggered my asthma and a headache on the several occasions when it was being tested.

I understand the desire to use MDF but normal non-Laser MDF certainly is banned and if you wish we can have a meeting and demo of why this is the case with other interested parties, however we’ve already tested MDF, it was one of the first things we tested.

While most public places will laser MDF, that is at their own risk and doesn’t mean that it is best practice, none of the colleges I’ve worked at or visited including, all 5 colleges of University of the Arts, University for the Creative Arts, and Royal College of Art.

Also FYI: The lens in our laser cutter can’t focus materials greater than 12mm so it is impossible that 18mm be cut.


AC synchronous clock
(l_shearer) #4

Okay, this is progress.

Let’s break it down a bit;

  1. The MDF smoked a lot.
    MDF will smoke when lasercut mostly from combustion of wood particulate, not glues. anything that increases the absorption of heat into the material causes this, specifically;
  • slow feedrate
  • poor laser focus
  • insufficient laser power to cut completely
  • moisture in the material
  • inappropriate thickness of material
  • Glue used by manufacturer
  • inappropriate workpiece height
  • movement aberrations (particularly if the laser “lingers” or has excess travel)

Essentially anything that causes heat to be absorbed into the material without either removing that hot material, or moving on before it can cool, will cause smoke.

All of this may be significantly different from the prior experience.

  1. Anything with glue in it will block the filter
    Firstly, as above I think that particulate matter, not glue, is the main issue with smoke from MDF and plywood.

Although glues may block the filter they wouldn’t be acting as a glue, so much as a fine/microscopic post-vapourised powder (Which is what the filter is meant to catch) and they represent only a small amount of the material removed by the laser.

As an aside, addressing issues of cutting quickly with high, focussed power should resilient mostly in gaseous vapours and monomers rather than Microparticles. This is also what happens to acrylic/MMA (vaporisation and decomposition, with gasseous remains) when you laser it.

If pricing for filter change (rather than washing) is the issue, is differential pricing possible?

The price for use of the machine is already approaching 1p / second. Forbidding nearly all forms of cheap, available material (I.e plywood, mdf, particleboard) is going to limit the use further and drive up cost.

MDF is surely to be banned from any cnc router and hand working currently, iirc, so that is not an option either.


(Richard Stephens) #5

For what its worth the make[r]space in cambridge doesnt permit its members to cut mdf on its laser machines either.

http://wiki.makespace.org/Equipment/Laser_Cutter


(Tom Lynch) #6

I think you’ve misread that, it quite clearly says not to cut it…

Can I cut it?

Woody things

Wood: yes! (be careful of fire)
Plywood: yes if it is “laser ply”. Normal plywood has non-laser compatible glue
MDF: no. Clogs up our filters and smells bad.
LaserMDF: no. It produces perhaps 50% the gunk of MDF but still too much.
Cork: yes. Let us know how it goes!

Also:

9mm MDF (note: do not cut MDF - see above!)


(Tom Newsom) #7

He said doesn’t :smiley:


(Tom Lynch) #8

Sozzles @Rs1771


(Tom Newsom) #9

Further research says it’s the formaldehyde glues that are unkind to the cutter and your lungs. “Laser grade” MDF is made with better glue and can probably be permitted. We should get some and test it.


(Tom Lynch) #10

It still blocks the filters @tomnewsom it still has horrible fumes… I’ve used it before. We can try it I guess.


(Rich Maynard) #11

I think laser grade mdf has less formaldehyde, not no formaldehyde.


(Tom Lynch) #12

The issue with MDF was based on actually trying it rather than reading about it… It was horrible… I would suggest we look at the SDS for Laser MDF and try it but I would be less than excited to use it as of my past experiences with Laser MDF and normal MDF.


(Robin Thomson) #13

I just thought I’d chip in with my experience as a technician in design technology at a State Secondary school. We have a 40w laser cutter and use it to cut acrylic, HIPS, various grades of card, ply and MDF on a regular basis. We have also cut fabrics, paper, felt, polypropylene (the manufacturer lists settings for cutting these) and have etched on wood based materials and acrylic.

By the evidence of sight only, MDFseems to produce about as much smoke as ply but the smell is different - more pungent, and especially strong when cutting thicknesses above 6mm or when the lenses and mirrors are due for a clean. Any smoke is the enemy of clean lenses.

We wash out the bed a couple of time a year and the filter is changed annually. It is important to clear the bed regularly as off-cut particles can accumulate under the honeycomb and these scraps, especially of wood, card or paper present the greatest fire hazard (spoken from experience!).

I’m not sure what survives the filtering process when MDF is cut but I agree the smell suggests something nasty. This is much reduced when cutting 3mm and 4mm however, perhaps because of the faster rate of cutting.

In my earlier career in furniture-making it was airborne dust (with it’s cargo of formaldehyde) from machining MDF that was of most concern. It was obvious that dust escaped the extraction and hung in the air for hours. We would wear dust-masks whenever any MDF was being worked on but it would remain in evidence on surfaces and impregnate work clothes.

I did some work with “zero” formaldehyde MDF (some products for Japan whose import regulations banned regular MDF). I don’t know if this what is marketed as “laser MDF”. Its physical properties seemed to be identical - but it was twice the price.


(Sarah Barber) #14

Can I get some clarification - is the use of MDF banned for the laser cutter only? What about cutting it with power tools such as a jigsaw? What about hand tools?


(Tom Newsom) #15

Just be sure to wear a face mask


(Dermot Jones) #16

Great to have your input and experience here @robinT

The zerp formaldehyde MDF sounds promising.

Seems to me like it’s worthwhile experimenting with normal MDF now the cutter has be refurbished and take things from there.

We may have overreacted to one very unpleasant experience caused by a failing machine.

The maintenance implications of MDF need consideration too. Perhaps that involves paying more to use it, as has been mentioned earlier.


(Tom Lynch) #17

FPP3 Dust Mask for all in the area. Really until we have to space with a dedicated area and air purification we shouldn’t really do MDF work because it will just settle down everywhere and get aerated when people brush it.


(Tom Newsom) #18

Having someone hold the sucky end of the Henry next to the cutting operation can help cut down on airborne dust.


(Tom Lynch) #19

Yes, except the henry hasn’t got a hepa filter and if it did it would block in a few minutes of use.


(Richard Stephens) #20

MDF dust settling on surfaces is an absolute bugger, although if you are cutting with a jigsaw or some other thin blade, it really doesn’t generate much volume of dust. Health-wise, best thing is to wear a mask, and keep it on even after you’ve finished cutting as the smallest particles stay in the air. There are some old damp bits of mdf in the phase 2 area that need cutting up a bit to be transported to the skip.